Brain shunt

概述

A brain shunt drains built-up fluid from the brain to another part of the body, helping relieve pressure in the brain.

Every day, the brain makes about 2 cups (500 milliliters) of cerebrospinal fluid (CSF). This fluid flows through deep cavities in the brain called ventricles. It also flows around the brain and spinal cord. CSF cushions, protects and nourishes the central nervous system.

When the fluid can't circulate as it should, it builds up. This buildup is called hydrocephalus. It can happen if something is blocking the fluid. It also can happen if the brain makes too much fluid or the body doesn't absorb it well.

Hydrocephalus can increase pressure inside the skull, harming brain function. Sometimes, fluid buildup enlarges the ventricles without raising the pressure level, which can also cause issues. This is called normal-pressure hydrocephalus.

A shunt helps drain the built-up fluid to another part of the body, where it can be absorbed safely. People who have a shunt in place typically need it for the rest of their lives. They require regular monitoring.

Types

There are several types of shunts. All types consist of two flexible tubes called catheters that are attached to a valve.

A short upper catheter is placed in one of the brain's ventricles and attached to one end of the valve. This catheter is also called the ventricular catheter. The other end of the valve is attached to a longer catheter. This lower catheter is directed under the skin to another part of the body such as the abdomen or a heart chamber. This area is known as the drainage site.

The valve controls the rate of CSF flow from the brain to the drainage site. This allows the fluid to be absorbed elsewhere and relieves pressure on the brain.

Types of brain shunts are named for where the fluid is drained:

• A ventriculoperitoneal (VP) shunt drains fluid to the abdomen. This is the most common type. The shunt drains into the space inside the abdomen but outside the abdominal organs. This space, called the peritoneal cavity, efficiently absorbs extra fluid and is easy to access surgically. It's also large enough to fit extra tubing. When a shunt is placed in a child, extra tubing allows for childhood growth.
• A ventriculoatrial (VA) shunt drains fluid to the heart. It's used when the abdomen isn't an option.
• A ventriculopleural (VPL) shunt drains fluid to the chest cavity. This type of shunt is less common due to the risk of fluid buildup in the lungs.
• A ventriculosubgaleal (VSG) shunt may be a temporary option for newborns. Fluid collects under the scalp and is absorbed by the body.

An alternative to a brain shunt is a lower spine shunt, called a lumboperitoneal (LP) shunt. It drains fluid from the lower spine to the abdomen. It's used less often than brain shunts.

The valve is a one-way system that controls fluid outflow from the brain. It's usually placed beneath the scalp either behind the ear or closer to the top of the head. The valve opens when the pressure in the ventricle becomes greater than a set value. As fluid drains, the pressure falls, letting the valve close until the pressure rises again. Different valve options are available:

• Fixed valves. These are the simplest and oldest types of shunt valves. They come with different preset pressure levels, such as low or medium pressure. A limitation of this design is that if the valve setting causes too much or too little fluid drainage, another surgery is required to replace the valve.
• Programmable valves. These valves allow the opening pressure to be adjusted without surgery, using an external device. A magnetic programmer is used to change the valve's pressure settings as a person's needs change. On older models, exposure to strong magnets, such as MRI, could inadvertently change the settings. Newer models are designed to prevent such changes.
• Antisiphon valves. These valves increase resistance to the flow of CSF when you stand up. This can prevent too much drainage when you move from lying or sitting to standing. Antisiphon valves may be especially helpful for people who are taller, larger or more active than average.
• Flow-regulated valves. These valves aim to maintain a constant flow of CSF, regardless of pressure changes inside the brain.
• Combined valves. These valves combine different technologies, such as adjustable pressure settings and antisiphon features, into a single device.

Valves are similar in terms of how well they work and how long they last. Talk about your options with members of your healthcare team. They can help you decide what might work well for your circumstances.

目的

Brain shunts frequently are used to treat different types of hydrocephalus. Brain shunts also can treat conditions marked by increased pressure in the brain, such as idiopathic intracranial hypertension.

Hydrocephalus

Hydrocephalus can have many causes. It also can affect people of all ages, including infants and older adults.

Hydrocephalus in infants can happen because of several factors:

• The central nervous system develops in a way that blocks the flow of cerebrospinal fluid. For example, some babies develop a neural tube defect such as spina bifida. Or they develop Chiari malformation, a condition in which brain tissue extends into the spinal canal.
• An infection, such as meningitis, happens in the uterus or during childbirth. The infection can scar brain tissue and block the flow of CSF.
• If a baby is born prematurely, bleeding may occur within the ventricle, causing hydrocephalus.

Normal-pressure hydrocephalus (NPH) is a specific type of hydrocephalus that enlarges the brain's ventricles and pushes against brain tissue. But it doesn't change the pressure level in the brain. Normal-pressure hydrocephalus without a clear cause occurs mostly in older adults. Common symptoms are chronic difficulties with thinking and remembering, worsening in your walking, and urinary incontinence.

Hydrocephalus also may result from:

• Complications of stroke or brain bleeding, specifically a type of bleeding in the brain called subarachnoid hemorrhage.
• Brain tumor.
• Infections in the brain.
• Traumatic head injury.

Some adults and children with hydrocephalus who don't have symptoms or whose condition isn't getting worse may not need a shunt. Instead, they may choose watchful waiting, with regular checkups and imaging tests.

For some people, a procedure called endoscopic third ventriculostomy (ETV) may be an alternative to shunt placement. This procedure uses a tiny tube with a camera on the end called an endoscope. During ETV surgery, the endoscope allows the surgeon to make a small hole in one of the ventricles. Excess CSF can then drain out of the hole.

Idiopathic intracranial hypertension

A brain shunt may be used to relieve increased pressure in the brain, also known as intracranial pressure. For example, a shunt may be used for a condition called idiopathic intracranial hypertension (IIH), which used to be called pseudotumor cerebri. This condition is marked by an unexplained rise in intracranial pressure that often causes vision difficulties. A shunt is generally considered for IIH only if other treatments haven't relieved symptoms.

风险

While shunts are lifesaving, they typically require lifelong management. There are risks of side effects both in the short and long term.

• Pain after surgery. After surgery to place the shunt, you may feel pain and soreness at the incision sites and possibly along the path of the shunt tubing or in the abdomen.
• Bleeding. Bleeding in the brain may occur.
• Shunt infection. There's a risk that the shunt becomes infected. If it does, infection typically develops about 2 to 6 weeks after shunt placement. Symptoms may include headache, feeling unwell, nausea, vomiting and fever.
• Underdrainage. Sometimes not enough fluid is removed, and symptoms of hydrocephalus return or worsen.
• Overdrainage. Too much fluid removal can cause headaches and bleeding in the brain. The ventricles can collapse, causing blood vessels to tear and blood to collect just below the lining of the brain. This is called a subdural hematoma.
• Mechanical failure. One of the biggest long-term risks of brain shunts is that they stop working. Tubes can become blocked, disconnected, move or break. These are the most common reasons for a shunt replacement. Most shunts that are first placed during infancy need to be replaced within 10 years.
• Other complications. Rare issues include allergic reactions to shunt materials, bleeding or abdominal problems. Seizures may occur but aren't always related to the shunt. Complications of shunts can be fatal, but this is rare.

In adults, having other chronic conditions, such as heart or kidney disease, diabetes, or a history of stroke, may increase the risk of complications around shunt surgery.

如何进行准备

Your surgeon may request imaging tests beforehand, such as a brain MRI or a CT scan, to plan the procedure. In some cases, a temporary drainage system such as a lumbar drain or an external ventricular drain is used first to see if a permanent shunt is needed.

Consider what kind of help you might need when you leave the hospital. You'll need a ride home. If you live alone, it may be helpful to have someone stay with you for a few days to help with everyday tasks. Most people need a few weeks to recover fully.

Food and medications

Follow the instructions from your healthcare team about what to do in the days and hours before the shunt procedure. You may have restrictions on what you can eat or drink the hours before your surgery.

You may need to stop certain medicines. For example, blood-thinning medicines slow the blood-clotting process. These medicines can increase the risk of bleeding and need to be stopped at least temporarily before surgery. Talk to your healthcare team about when to stop taking blood-thinning medicine before surgery and for how long.

Clothing and personal items

Your care team may recommend that you bring several items to the hospital, including:

• A list of your medicines.
• Eyeglasses, hearing aids or dentures.
• Personal care items, such as a brush, a comb, a shaving kit and a toothbrush.
• Loose, comfortable clothing.
• A copy of your advance directive. This is a legal document. It includes instructions about the kinds of treatments you want or don't want in case you are not able to express your wishes.
• Items that help you relax, such as portable music players or books.

During shunt surgery, do not wear:

• Contact lenses.
• Dentures.
• Eyeglasses.
• Jewelry.
• Nail polish.

可能出现的情况

A shunt procedure usually is done in a hospital. The surgery itself isn't long, but your healthcare team will want to watch you for any complications and make sure you're well enough to go home. Most people stay in the hospital a day or two after surgery.

Before

Before surgery, you may meet with members of your surgical team, such as your neurosurgeon and the anesthesiologist, who keeps you from feeling pain during the procedure. In some cases, the abdominal portion of the surgery is done by a general surgeon using minimally invasive techniques. Other team members help you with hospital paperwork, check your vital signs and help you get ready for the operating room.

Typically, you have general anesthesia during surgery. That means you will be completely asleep. The actual surgery takes only about 30 minutes. Going to sleep and waking up adds about an hour.

A small spot on your head may be shaved and scrubbed with an antiseptic solution to get rid of germs and help prevent infection. This spot is where the upper catheter goes into the brain ventricle. The spot where the lower catheter is put in also is scrubbed clean. This is usually on the abdomen for a VP shunt or around the collarbone for a VA shunt.

You also may receive antibiotics before the surgery, to prevent infection of the shunt.

During

During a typical brain shunt procedure, the surgical team:

• Makes small incisions in the head and the area where the catheter will drain, typically the abdomen.
• Drills a hole in the skull to allow the upper catheter to be placed in the brain's ventricle.
• Creates a tunnel under the skin from the head to the drainage site.
• Pushes the lower catheter through the tunnel to the drainage site and removes the tunneling device.
• Connects the lower catheter to the valve.
• Passes the upper catheter through the hole in the skull and places it in the brain's ventricles and connects it to the valve.
• Confirms the flow of cerebrospinal fluid from the brain ventricle to the drainage site once the shunt is assembled.
• Closes the incisions and puts sterile dressings on the incisions.

Your surgery team takes care to avoid possible contamination of the shunt with germs.

After

You'll be monitored in the hospital for 1 to 2 days. Imaging may be done to confirm that the shunt is working. You'll receive instructions on caring for the incisions. Your healthcare team also may tell you what signs of complications to watch for.

Outpatient physical therapy after surgery may be part of your care. It helps strengthen your legs and ability to walk. It also may help retrain your balance. Physical therapy may be particularly helpful for older adults. Getting the most benefit from the shunt can take several months. A small number of people need to have rehabilitation treatments after surgery while they are in the hospital.

结果

Shunt placement is an effective treatment for most people. If recovery is going well and there are no shunt complications, most people can return to regular routines within weeks of surgery.

A follow-up visit is usually scheduled for a few weeks after surgery and then again in 3 to 6 months. Follow-up appointments may include an imaging exam, such as a CT scan or an MRI.

In children with hydrocephalus, shunts greatly improve survival. Most children can go to school and play sports, although some may have restrictions on contact sports.

Adults with normal-pressure hydrocephalus often experience improvements in their thinking and memory skills, walking and social abilities within 6 to 12 months after shunt placement.

Once you have a shunt, it's typical to always have a shunt unless it's removed because of infection. Lifelong follow-up is a must. Shunts may need adjustments or revisions over time. Infants and children who receive a shunt often require a replacement as they grow.

When to call your doctor

Complications of shunts require prompt attention. The most common complications involve the shunt becoming infected or not working properly. Another surgery or other interventions may be needed.

Call 911 or seek emergency medical care for any of the following symptoms:

• Signs of infection, including a temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, chills, tenderness around the shoulder or neck, headache, or swelling or drainage at the incision sites.
• Vision difficulties, such as eyes fixed downward, or blurred or double vision.
• In infants, an unusually large head, rapid increase in the size of the head or a bulging "soft spot" on the top of the head.
• Increased sleepiness, lack of energy, or personality changes. Infants might be more irritable than usual or have a high-pitched cry.
• Headache, seizures or memory loss.
• Problems with balance, coordination or walking.
• Upset stomach, throwing up or changes in eating patterns.

Also, talk to your healthcare team right away if you notice signs of delayed development in your child.